var_dump（$ nombre）打印两次ajax + php slim框架为什么？

I´ve my call a ajax

$("#box-modal").on("shown",function(event)
   {
       $("button#add-cart").click(function()
       {

           if($("#selectproductname").val()!=='-1')
           {
                var valueidproduct = $("#inputidproducto").val();
                var request = $.ajax({
                    type:'POST',
                    url: '/lineorder/addCart/'+valueidproduct,
                    data: $("#form-product").serialize(),
                    datatype:'html'
                    });
                request.done(function(html) {
                    $( "#editor-panel > div" ).html( html);
                });

                request.fail(function( jqXHR, textStatus ) {
                    alert( "Request failed: " + textStatus );
                });
            }

When I call a my route php, and I want to get the result of a variable print two times why?. I only want one time.

$app->post('/lineorder/addCart/:id',function($id) use($app)
{
       $str='';
       //compruebo si el array de sesion del carrito era creado si no es creado procedemos a crearlo
       if(!isset($_SESSION['cart-items']))
       {

           $_SESSION['cart-items'] = array();
       }
       $cantidad = $app->request()->post('inputcantidad');
       $nombre = $app->request()->post('inputnombre');
       var_dump($nombre);die();

In my

request.done(function(html)
{
   $("#editor-panel > div").html(html);
}

print two times the result;

What´s the fix? What I do wrong?